Bromate determination in water using chlorpromazine after correction of chlorinating agents and humic substances interference

ISSN 1061-9348, Journal of Analytical Chemistry, 2007, Vol. 62, No. 11, pp. 1055–1063. Pleiades Publishing, Ltd., 2007.ARTICLESBromate Determination in Water Using Chlorpromazineafter Correction of Chlorinating Agents and Humic Substances Interference1M. G. MitrakasLaboratory of Analytical Chemistry, Chemical Engineering Department, School of Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 Greece
Received April 28, 2006; in final form, February 16, 2007
Abstract—The presence of soluble humic substances and chlorinating agents interfered positively with the
spectrophotometric determination of bromate ( BrO ) using chlorpromazine. Removal of the soluble humic
substances through their precipitation by a basic lead acetate (15.9 g/L Pb(CH3COO)2 · 3H2O—4.7 g/L PbO)solution corrected their interference effectively. In addition, the use of NaHSO
2–OCl , and Cl2–NH2Cl, when present in concentrations of up to 1.5, 3.5, and
3.5 mg/L, respectively. Thus, the spectrophometric method was rendered suitable for the direct bromate deter-mination in natural, chlorinated, and ozonated waters, since the application to such samples resulted in the accu-
rate and precise determination of bromate. The method’s detection limit was estimated as 1.6 µg /L
the linear range of the calibration curve was extended up to 700 µg BrO /L. The method also gave results com-
parable to those obtained by the well-established ion chromatographic method and had the additional advantageof being simple, rapid, low cost, and suitable for brackish water.DOI: 10.1134/S1061934807110093
Ozonation can improve the odor and taste of drink-
method. IC, however, is not free from weaknesses and
ing water effectively, remove coloration, oxidize fer-
difficulties, the main one being chloride interference [5,
rous and manganous ions, and mainly destroy microor-
6]. Weinberg (1994) overcame this problem by using a
ganisms. Thus, it appears as a promising alternative dis-
silver cation resin and a chelation column to remove
infection method for drinking water. Ozone, however,
leached silver, in order to protect the separation col-
also oxidizes bromide (Br–) to bromate (BrO– ). The
umn. The detection limit of the method was 0.5 µg/L
after the application of a preconcentration technique.
latter has been considered as a potential carcinogen and
Since the established maximum contaminant level of
has been classified in Group 2B by the International
bromate has been set at a very low value (10 µg/L), all
Agency of Research on Cancer (IARC). The World
proposed methods for bromate quantification focus on
Health Organization (WHO) recommended the provi-sional guideline value of 25 µg/L, which is associated
achieving high selectivity, sensitivity, and low detectionlimit [7–9].
with an excess lifetime cancer risk of 7 × 10–5. Sincebromate ion is considered as a hazardous substance, the
Due to certain difficulties involved with the IC
European Community [1] and USEPA [2] have estab-
method, simpler and cheaper spectrophotometric BrO–3
lished the value of 10 µg BrO– /L as the maximum con-
determination was sought and proposed. The method
employed chlorpromazine [10] and other phenothiaz-
The impact of bromate on human health has resulted
ines [11] as color-producing reagents and seemed to be
in the appearance of several publications during the last
an interesting and attractive alternative method. In an
decade dealing with the analytical methods of bromate
acidic environment, phenothiazines are oxidized by
determination in potable waters and possible interfer-
BrO– to form stable, colored cations. This method [10–
ences [2–6]. The commonly used method for bromate
determination is ion chromatography (IC), which has
12] had a low detection limit and no interference by Cl–
been standardized and considered as a reference
and other anions and cations commonly present in nat-ural water. Since its development, the method was
1 The text was submitted by the author in English.
applied in only one case to natural water samples as
post-column bromate determination following IC sepa-
water in a 1-L cylinder-shaped vessel equipped with a
ration [13]. Recently, Mitrakas and coworkers [12]
porous glass diffuser. Ozone was generated from 99.5%
tried to apply the method to natural water samples, but
pure oxygen. The distilled-deionized water was
found that the presence of soluble humic substances
adjusted to pH < 3 with H2SO4 to prevent ozone decom-
resulted in positive interference giving high pseudo-
position. The ozone concentration in the stock solution
bromate values, thus rendering the method unsuitable
(typically about 18 mg/L) was measured by the iodo-
for bromate determination in natural water and restrict-
metric method [16]. An aliquot of the ozone stock solu-
ing its use in pure bromate solutions. The positive inter-
tion (10–50 mL) was mixed with 2 L of the water sam-
ference was attributed to the electron acceptor groups
ple. Bromate was determined at least 24 h after sample
invariably existing in the humic molecules serving as
ozonation when any molecular ozone, hydroxyl, and
bicarbonate radicals were not present.
Removal of soluble humic substances can, in theory,
be achieved either through the use of membrane filtersof the appropriate pore size or by means of various floc-
Total Organic Carbon (TOC)
culants or precipitants (inorganic salts), which have
A Shimadzu 500 TOC analyzer was used.
been used successfully in various cases for the removalof suspended organic materials from liquids. In addi-tion, chlorpromazine and other phenothiazines are also
2 [11], which can be effectively removed by sulfite
Bromate. A 1000 mg/L BrO stock solution was
prepared by dissolving the appropriate amount of thereagent-grade KBrO in distilled-deionized water and
Since the spectrophotometric method of BrO–
stored at 4°C. Working standards were daily prepared
determination using chlorpromazine seems to be a sat-
by proper dilution of the stock solution. Chlorprom-
isfactory alternative to the IC method, this study was
azine (CLP). A 1200 mg/L solution was prepared by
undertaken with the following objectives:
dissolving the appropriate amount of reagent in dis-
tilled-deionized water. Keeping the CLP solution
—various techniques (filtration, precipitation) in
refrigerated in a dark bottle resulted in a lifetime greater
than 3 months. Nitrite. Standard and working solutions
—sulfite ion in removing chlorinating agents; and
were prepared, standardized, and assayed as describedby the standard methods [16]. Sulfamic acid. A 1 M
• to propose a procedure which would permit the
solution of NH2SO3H was used. Sodium bisulfite. A
accurate determination of BrO– , thus rendering the
0.2 g/100 mL solution (pH 4.2) was daily prepared by
spectrophotometric method suitable for application to
dissolving reagent-grade NaHSO3 in oxygen-free cool
ozonated, chlorinated, and natural water. The results
water and kept in the dark. Natural organics. The
will be substantiated by using IC as a reference method.
sodium salt of humic acid (Aldrich, H1675–2, LotNumber 16308) was used for simulating the presenceof soluble natural humic substances. Hydrochloricacid. Analytical grade HCl from Baker, stored in a glass
Natural water samples. Ten natural water samples
bottle, was used, because it gave the lowest bromate
were collected from Northern Greece and will be
referred to as samples N1–N10 henceforth. Treatmentof the samples included filtration through a 0.45-µmpore-size membrane filter, ozonation, and/or chlorina-
tion. Chlorinating agents were added to ozonated water
Iron chloride [FeCl ], aluminum sulfate [Al (SO ) ],
after excess ozone removal by rapid filtration through
granular activated carbon. Bromate, however, was
and basic lead acetate at different concentrations were
determined at least 24 h after any disinfection treat-
used. The latter is used in sugar factories as an extract-
ant and to remove suspended organic matter fromsugar-beet sap. Since the former two reagents did not
Artificial water. Background ions included sodium
control the interference effectively, while the latter did
bicarbonate 5 × 10–3 M, calcium chloride 5 × 10–4 M,
(see Results and Discussion), it was adopted as the pre-
and sodium sulfate 5 × 10–4 M were dissolved in
cipitant in the proposed procedure and composed of
organic-free distilled-deionized water (pH 7.8 ± 0.1) to
15.9 g/L Pb(CH3COO)2 · 3H2O and 4.7 g/L PbO. For its
simulate representative freshwater conditions.
preparation, the reagents were dissolved in the appro-
Ozonation procedure. An Ozonia® Triogen Model
priate volume of distilled water under continuous stir-
Compact TOGC2A ozone generator was used. The
ring for approximately 24 h, the suspension was left for
ozone stock solution was prepared batchwise by bub-
sedimentation, and the supernatant clear solution was
bling ozone through organic-free distilled-deionized
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
BROMATE DETERMINATION IN WATER USING CHLORPROMAZINE
prepared by proper dilution and standardized using theDPD colorimetric method [16].Sodium hypochlorite. A Riedel de Haen stock solu-
tion was used. A chlorine solution of about 100 mg/L was
Sodium chlorate. A 1000 mg/L ClO stock solu-
daily prepared by proper dilution of the stock solution
tion was prepared by dissolving the appropriate amount
in distilled-deionized water and standardized by a
of reagent-grade NaClO3 in distilled-deionized water.
0.01 N standard sodium thiosulfate titrant. Working
Working standards were prepared by proper dilution of
cial water were prepared from a chlorine solution and
Sodium perchlorate. A 1000 mg/L ClO– stock
standardized using the DPD colorimetric method [16].
solution was prepared by dissolving the appropriate
Chloramine stock solution. A 200 mg/L Cl
deionized water. Working standards were prepared by
2Cl nominal concentration solution was prepared on
the day of the experiments by mixing NaOCl and
proper dilution of the stock solution.
(NH4)2SO4 stock solutions in distilled-deionized waterat 4 : 1 chlorine to ammonium—nitrogen mass ratio
(0.8 : 1 on a molar basis). To obtain the highestmonochloramine yield and minimize ammonia volatil-
Spectrophotometry.Instrumentation. A Lambda 2
UV/VIS spectrophotometer version 3.7 Perkin Elmer
adjusted to pH 8.3 with either 0.5 M H2SO4 or 1 MNaOH before mixing and the NaOCl solution was
Procedure. (1) A 40-mL water sample was mixed
with 3 mL of a basic lead acetate solution (correspond-
ing to the final lead concentration of about 865 mg/L),
preparation of the chloramine stock solution, pH was
agitated gently for 5 min, and the suspension was fil-
maintained at 8.3. Working standards in the range of 1–
tered through a 0.45-µm pore-size membrane filter.
5 mg/L Cl2–NH2Cl in artificial water were prepared by
Stirring gently, the following reagents were added to
proper dilution of the chloramine stock solution and
the clear sample solution: (2) 0.1 mL of 0.5 M HCL and
standardized using the DPD colorimetric method [16].
0.1 mL of sodium bisulfite solution, followed by 5 mincontact time for chlorinating agents removal; (3) 0.1 mL
Sodium chlorite. A 100 mg/L ClO– nominal con-
of 1.5 M KOH, followed by 5 min contact time for oxi-
centration solution was prepared by dilution of 168 mg
dation of a significant part of the excess sodium
sodium chlorite of AGROS (80% in NaClO2) in dis-
bisulfite; (4) 0.5 mL sulfamic acid solution, followed by
tilled-deionized water. Solution pH was maintained at
3 min contact time for nitrite removal; and (5) 5 mL of
higher than 7, thereby minimizing the potential conver-
CLP solution and 4 mL acid catalyst (concentrated
sion of ClO– to ClO– . This stock solution was stored
HCl), followed by 5 min contact time for color devel-
opment. The absorbance was measured at 527 nm in
in an amber bottle in a cool, dark location. The titer of
10-cm path-length measurement cells.
the stock was quantified daily by a 0.01 N standardsodium thiosulfate titrant [16]. Working standards in
Ion chromatography. The analysis was carried out
using a Dionex 4500I Ion Chromatograph under the
the range of 1–5 mg/L ClO– in artificial water were
below 10 µg/L. An overlap of bromate by chloride innatural water samples was observed. This overlap was
attributed to the high injection volume, since bicarbon-
Certain comments concerning the IC reference
ate content of the samples influenced the ratio of
method need to be mentioned. The linear regression
equation of the calibration curve, in the range of 5–
(HCO /CO ) in the eluent significantly, which in turn
decreased the retention time of chloride. This overlap-
ping was overcome by converting HCO of the natural
The detection limit was about 5 µg/L and the method
water samples to CO with the addition of an equiva-
showed poor repeatability for BrO– concentrations
lent amount of 1 M NaOH (meq OH– = meq HCO– ).
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
water after its ozonation. All this implies that, if the
interference was controlled, the spectrophotometricdetermination of bromate could become a successful
and an easy-to-apply method compared to the alterna-
Tests pertaining to the elimination of the interfer-
ence were conducted on ten natural water samples prior
to their ozonation. These samples analyzed using the
reference IC method showed no bromate concentration
(below the detection limit of 5 µg/L), while the directspectrophotometric method gave unrealistic high
pseudo-bromate concentrations ranging between 10and 40 µg/L, due to the presence of soluble humic sub-
stances, as was the case in a previous study [12].
Attempts to remove soluble humic substances, by pass-ing the samples through a 5,000-Dalton pore-size mem-
An example (sample N3 prior to ozonation) of the effect of
brane filter, failed to screen them out effectively. The
different precipitants on the interference of soluble humic
results also showed that neither ferric nor aluminum
substances in the spectrophotometric determination of bro-mate. The quantity of the precipitant is shown in the
salts at various concentrations were effective means in
abscissa in terms of the corresponding metal concentration.
precipitating humic substances quantitatively, sincebromate pseudo-concentrations still persisted in allsamples after this treatment. An example of this effect
Chlorinating agents NH2Cl and NaOCl were removed
on sample N3 is shown in the figure. On the contrary,
with the addition of sulfite ion in amounts stoichiomet-
the use of a basic lead acetate solution at the quantity
rically equal to their concentration in water samples
mentioned in the proposed procedure (see Experimen-
(see section on chlorinating agents—background).
tal) resulted in an effective control of humic substanceinterference in the determination of bromate by CLP,
since pseudo-bromate levels were suppressed below thedetection limit in all samples. An example of this sup-
Interference and their correction.Humic sub-
pression in sample No 3 is shown in the figure. The tests
stances. A recent study has shown that soluble humic
with the basic lead acetate solution were extended to
substances, invariably existing in natural water, inter-
pure humic acid solutions prepared in distilled-deion-
fered positively, giving high pseudo-bromate values,
ized water to simulate the presence of natural organics
thus rendering the method unsuitable for bromate
in water (Table 1). All humic acid solutions showed
determination in natural water [12]. In addition, this
pseudo-bromate concentrations when the CLP method
interference would also overestimate bromate in drink-
was directly applied without any treatment with a pre-
ing water, since humic substances can persist in the
cipitant. When, however, the proposed procedure wasapplied to artificial humic acid solutions in concentra-tion up to 5 mg/L, no bromate concentrations were
Table 1. Pseudo-bromate concentrations determined in stan-
determined (Table 1). Consequently, these experiments
dard humic acid solutions using CLP and their correction by
provided strong evidence that the use of a basic lead
acetate solution could effectively control the interfer-ence of humic substances in bromate determination
Pseudo-bromate concentration, µg Br O /L
using phenothiazines. The superiority of Pb relative to
Fe and Al in removing humic substances can be attrib-
uted to the nature of the cation and to the maintenanceof the sample pH in the range 5.5 to 6.5 upon the addi-
tion of the basic lead acetate solution (Table 2). In con-
trast, the addition of the other two metal salts lowers thesample pH in a more acidic region. It is known that
divalent and trivalent metals form chelates with humic
substances and the stability constant of Pb chelates ishigher than for the other two metals at the pH range 5
to 6.5 [17]. In addition, most of Pb chelates at this Pb
concentration are water insoluble [17, 18]. Therefore,they are effectively removed from the samples.Nitrite. Nitrite exhibits a strong interference in
BDL: Below detection limit = 1.6 µg Br O /L.
bromate determination with CLP (Eq. (2)). This
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
BROMATE DETERMINATION IN WATER USING CHLORPROMAZINE
Table 2. pH changes in the various steps of the proposed method as a dependence of bicarbonate concentration of artificialwater samplesTable 3. Control of nitrite interference in the proposed method and the influence of contact timea and bicarbonate concen-tration
a Time lapsed between sulfamic acid and acid catalyst addition.
c 25 ± 1 indicate the result within the absolute precision.
interference is usually controlled with sulfamic
radicals were not present. Preliminary experiments,
• The reaction of sulfamic acid with nitrite is favored
× 10–3, R2 = 0.999. [2] in an acidic environment.
• A significant loss in sensitivity was observed when
In the proposed procedure with ozonated water sam-
the acid catalyst (HCl) was added to the sample prior to
ples, sulfamic acid eliminated nitrite interference when
the addition of CLP, in agreement with Farrel et al. [11].
present in concentrations of up to 500 µg/L (Table 3),without any influence on the sensitivity of spectropho-
• Nitrite will still interfere when CLP, HCl, and sul-
tometric bromate determination. Ozonated water sam-
famic acid are added simultaneously.
ples were spiked with nitrite 24 h after their ozonation
In conclusion, the addition of 0.5 mL 1 M sulfamic
when any molecular ozone, hydroxyl, and bicarbonate
acid in a water sample after the removal of humic sub-
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
stances and before the addition of the acid catalyst,
The rate of reaction {4} is significant for practical
resulted in a pH value of about 2.5 ± 0.1, which favored
purposes in pH values lower than 4 [21].
nitrite destruction with no further loss of sensitivity,
Optimization of NaHSO3 addition. Preliminary
due to the CLP addition at this low pH value (Table 3).
studies showed that NaHSO , in concentrations of up to
It is self-obvious, however, that in water samples that
20 mg/L, when added simultaneously with CLP did not
do not contain nitrite, the addition of sulfamic acid can
interfere. These experiments have provided strong evi-
be omitted. The pH of the sample after sulfamic acid
dence that bromate selectively oxidizes CLP in the
addition is influenced by its bicarbonate concentration
presence of a sulfite ion. However, the suppression of
(Tables 2 and 3). Bicarbonate concentration in water
bromate sensitivity observed when NaHSO was added
samples between 1 and 8 × 10–3 M resulted in pH values
in water samples before sulfamic acid, was attributed to
lower than 2.6, promoting the fast destruction of nitrite.
partial bromate destruction (reaction (4)). Optimization
Higher bicarbonate levels resulted in pH values above
of the procedure at that step proved that:
2.7, which, in turn, significantly increased the reactiontime for nitrite removal (Table 3, line 8). A small paral-
• The addition of up to 5 mg/L NaHSO3 (Eq. (3)) did
lel displacement of the calibration curve was observed
not suppress the sensitivity of bromate (compare linear
when bicarbonate concentrations were greater than
regression Eqs. (3) and (10)), as well as the nitrite
10−2 M and it is, therefore, recommended that the stan-
removal presented in Table 3, when the time lapse
dards should contain similar bicarbonate levels.
between sulfamic acid and acid catalyst addition waskept at 3 min:
Background of chlorinating agents removal. The
most effective and widely used dechlorinating agent is
the sulfite ion. Since high pH values increase the reac-
• By increasing either the time lapse between sul-
tion rate of a sulfite ion with oxygen, NaHSO3 (stock
famic acid and acid catalyst addition at 5 min (Eq. (4))
solution pH 4.2) was selected as a dechlorinating agent
and 10 min (Eq. (5)) or NaHSO addition at 7.5 mg/L
2SO3 (stock solution pH 8.3), to minimize
(Eq. (6)), a suppression of bromate sensitivity was
the sulfite ion–oxygen reaction during the day.
observed because of the partial bromate destruction
Data in the literature indicate that reaction {1} is
immeasurably fast [19]. Reaction {2} of a sulfite ion
with monochloramine, as well as with NHCl
2 is completed in a matter of seconds [15]:
Optimization of Chlorinating Agent Removal
During the disinfection of drinking water, chlorine
As expected, chlorinating agents OCl– (Eq. (7)) and
dioxide (ClO2) reacts primarily by a one-electron oxi-
NH2Cl (Eq. (8)) interfered in bromate determination
dative pathway and, thus, the principal inorganic
with CLP. From oxychlorine residuals, the chlorite ion
byproduct is almost invariably chlorite ion (ClO– ) in a
(ClO ) also interfered (Eq. (9)), while the chlorate ion
nearly 70% yield [20]. Consequently, the chlorinating
agent’s interference control should mainly include the
(ClO ) and the perchlorate ion (ClO ) in concentra-
effective chlorite ion removal. The main reaction of the
tions up to 1 mg/L did not. The USEPA recommends
chlorite ion with the sulfite ion in the pH 4–7.5 region
that the combined residuals of ClO– , ClO– , and ClO–
must not exceed 1 mg/L in finished water.
This corresponds to a stoichiometry of two moles of
SO2– consumed for every mole of ClO– removed. In
the range of pH 4.5–5.5, the total removal of the chlo-
rite ion (i.e., >99%) was completed in less than 5 min[14] and the loss of the sulfite ion from the competing
By adding NaHSO3 before (pH region 7–8) or after
sulfite ion–oxygen reaction was minimized.
the removal of humic substances (pH region 5.5–6.5),
The sulfite ion, however, also reacts with the bro-
complete OCl–/NH2Cl and partial ClO removal was
mate ion. The reaction for the reduction of bromate by
observed (Table 4). After adjusting, however, pH at
value of 5, before adding the precipitant, bromatepseudo-concentrations were measured, although no
chlorine compounds were determined in any natural
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
BROMATE DETERMINATION IN WATER USING CHLORPROMAZINE
water samples, whether chlorinated or not. These bro-
Table 4. Influence of pH on the elimination of 0.5 mg/L var-
mate pseudo-concentrations were probably attributed
ious chlorine agents in artificial water, using 5 mg/L
to an ineffective humic substance removal by precipita-
tion at this low pH value. Consequently, the precipita-tion (step 1) must precede the chlorinating agent
removal. Experimental results showed that the addition
of 0.1 mL HCl 0.5 M in water samples after precipita-
tion decreased pH in the 5 ± 0.2 region, assuming thepresence of 1 to 8 × 10−3 M bicarbonate (Table 2). In
this pH region, rapid and effective elimination of
2Cl, OCl , and ClO was observed (Table 4). The
addition, on the other hand, of 0.1 mL KOH 1.5 M
assured a pH increase to a value higher than 8. In this
context, it should be noted that, at pH 8 and above, inthe presence of air, the rate of the sulfite ion–oxygen
reaction significantly increases [14]. Consequently,through the reaction with oxygen, the excess sulfite ion
concentration was effectively decreased, which, in turn,
minimized the bromate sensitivity suppression at step 4of the proposed procedure. When, finally, the proposed
* BDL: Below detection limit = 1.6 µg Br O /L.
procedure was applied to artificial solutions of chlori-
nating agents, the interference of OCl– up to 3.5 mg/L(Cl2–OCl–), of NH2Cl up to 3.5 mg/L (Cl2–NH2Cl), and
The detection limit of the method, calculated [22]
of ClO– up to 1.5 mg/L, was effectively eliminated.
from seven replicatations of 1–5 µg BrO– /L, was esti-
These values agree closely to the stoichiometry of reac-
tions (1), (2), and (3), respectively, and also with data
mated to be 1.6 µg BrO /L, in agreement with USEPA
presented in the literature [14, 15].
method 300 involving the separation and post-columncolorimetric determination of bromate with CLP [13].Bromate Determination in Ozonated Waters
• common ions in water such as K+, Ca2+, Mg2+,
The proposed procedure for bromate determination
NO– , and SO2– , in concentrations up to 500 mg/L, and
using CLP was also applied to ten ozonated and/or
chlorinated water samples in order to test its suitability
• trace elements such as F–, I–, Br–, Mn2+, Zn2+, Sr2+,
for bromate-containing samples and establish its ability
Al3+, and B in concentrations up to 500 µg/L, did not
to control interference. The bicarbonate content of the
interfere with the proposed procedure. These findings
samples ranged between 1.5 and 6.5 × 10–3 M, TOC
are in agreement with earlier reported results [10–12].
0.3–1.2 mg/L, while manganese and total iron were less
The presence of NaCl in concentrations of up to 3%
than 10 µg/L. No nitrites were measured after ozona-
did not interfere with the proposed procedure. This was
tion. All water samples were relatively low in total salt
an additional advantage of the proposed method in
content as judged by their specific electrical conductiv-
comparison to the IC method, rendering the spectro-
photometric method suitable for direct application inbrackish waters.
Bromate values obtained using the CLP method cor-
related closely with those obtained by ion chromatog-raphy (Table 5), indicating the accuracy of the method.Calibration Curve and Detection Limit
The regression lines had a slope and an intercept not
Due to the photosensitivity of blanks with chlorpro-
statistically different from 1 and 0, respectively, at the
mazine, distilled-deionized water was used as a blank
1% probability level. The method of bromate determi-
solution. The optimization procedure for CLP and HCl
nation with CLP also proved to be precise, since the
showed that, by using the proposed quantities, the high-
coefficient of variation (CV) was lower than 4% on
est precision and sensitivity for concentrations lower
average in the range of 25–100 µg BrO– /L (Table 5).
than 25 µg BrO– /L were achieved. The equation of the cal-
This means that the absolute precision at bromate con-
ibration curve in the linear range up to 700 µg ,
the reason that nitrite interference is considered to be
controlled when the bromate concentration w
abs = 23 × 10–4Xconc + 18 × 10–3,
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
Table 5. Determination of bromate in ozonated natural water samples by the spectrophotometric method using CLP vs anal-ysis by ion chromatography (IC)
a Coefficient of variation, estimated from 7 replicates.
b Significant at 1% probability level.
to be 25 ± 1 µg BrO– /L (Table 2). However, for the EC
• Nitrite was eliminated with sulfamic acid at pH 2.5 ±
0.1 (procedure step 4). Chlorinating agents and ozone,
and USEPA MCL of 10 µg BrO– /L, the absolute preci-
however, oxidize the nitrite of water to nitrate and, con-
sion was also about ±1 µg BrO– /L, since the CV was
sequently, they scarcely coexist, suggesting the bypass
between 6–9% in the range 2–10 µg /L.
Removal of interfering natural organics, nitrite,
chlorinating agents, and their byproducts is included in
In conclusion, as all interference parameters hardly
• In natural water as well as in chlorinated and ozo-
ever coexist, the proposed method could always be
nated water, naturally occurring humic substances
simplified by skipping the respective step of the pro-
strongly interfered in bromate determination with CLP,
cedure. The use of the spectrophotometric method for
and humic substances were effectively removed by
bromate determination gave accurate and precise
basic lead acetate (procedure step 1).
results that are similar to those obtained by the well-
• Chlorinating agents and their byproducts were
established chromatographic method. An additional
advantage of the spectrophotometric determination of
cedure steps 2 and 3). It is self-evident that, in nonchlo-
bromate using phenothiazines stems from its simplic-
rinated water, steps 2 and 3 can be omitted.
JOURNAL OF ANALYTICAL CHEMISTRY Vol. 62 No. 11 2007
BROMATE DETERMINATION IN WATER USING CHLORPROMAZINE
10. Gordon, G., Bubnis, B., Sweetin, D., and Kuo, C.A.,
Ozone Sci. Eng., 1994, vol. 16, p. 79.
The author is thankful to G. Kyriacou for his contri-
11. Farrel, S., Joa, F.J., and Pacey, E.G., Anal. Chim. Acta,
bution with the ion chromatography determinations and
V. Keramidas for his essential comments and editorialassistance.
12. Mitrakas, M., Tzimou-Tsitouridou, R., and Kerami-
das, V., Int. J. Environ. Anal. Chem., 2000, vol. 78,nos. 3–4, p. 343.
13. Walters, B. and Gordon, G., Anal. Chem., 1997, vol. 69,
1. Relating to the Quality of Water Intended for Human
14. Gordon, G., Slootmaekers, B., Tachiyashiki, S., and
Consumption, Directive 98/83/EC, 1998.
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